Although a culture and stain are very different tests, what they share in common is that they can be initiated when a patient is known to have an infection (as evidenced by elevated white blood count in a CBC, for example). A positive culure or stain will give definitive evidence to the physician not only that the patient has an infection, but the type of the infection -- bacteria, fungus, virus, or mycobacteria -- and exactly what kind of each of infection it is.

A negative culture or stain may mean that the patient does not have the condition the physician was searching for, or it may mean that there were no cells that reflected that condition within the sample collected. For this reason, multiple samples are frequently taken.

Here is a description of the test for tuberculosis.

Here is a description of a sputum culture.

Here is a description of the spinal stain.

A culture is when a sample of matter from the patient -- blood, sputum, urine, or spinal fluid (taken during a spinal tap) -- is placed in a container with substances that promote the growth of bacteria, fungi or viruses.

A stain is a similar test where some of the spinal fluid is spread and examined by a laboratory.

Because both of these tests need to be processed through a laboratory rather than examined by the physician immediately, there can be a significant delay in receiving the results. In the case of the culture, the delay can be caused by the need to wait for bacteria, fungi or viruses to grow.

Both cultures and stains are a way to get more information about the source of an undifferentiated infection. While there are a wide variety of infections that can be identified using cultures and stains, because of the higher cost of sending samples to a laboratory it is generally good practice to consider the patient's likelihood of having a more serious rather than viral infection.

Each potential bacteria, mycobacteria, fungus, or virus has its own test which must be ordered separately. Potential diagnoses include:

• Bacterial meningitis
• Fungal meningitis
• Mycobacterial meningitis (especially tuberculosis)
• Viral meningio-encephalitis
• Leukemic meningitis
• Leptospirosis

What is blood?

What are bacteria?

Fungi Overview

How Viruses Work

What are mycobacteria?

What is a culture?

What is a lumbar puncture?

What is meningitis?